Rotary code disk mounting structure for an optical encoder with an adhesive substance filling the circular recess of the spindle for adherence to said disk

ABSTRACT

The present invention is directed to a rotary code disk mounting structure for an optical encoder. A rotary code disk (3) with no center hole is fastened to a spindle (2) by an adhesive (J) that a is put in a recess (21) formed in a mounting surface (20). The mounting surface (20) is formed on the top surface of the spindle (2) with the central portion of the backside of the rotary code disk (3) in contact with the mounting surface (20). The rotary code disk mounting structure is applied to optical encoders for use in combination with servometers, machine tools and measuring apparatuses.

DESCRIPTION BACKGROUND OF THE INVENTION

The present invention relates to a structure for mounting a rotary codedisk on a rotary shaft of an optical encoder for use in combination witha servomotor, a machine tool or a measuring apparatus.

FIG. 4A is a schematic sectional view of a conventional rotary code diskmounting structure, FIG. 4B is an enlarged sectional view of anessential portion of the same rotary code disk mounting structure, andFIG. 4C is an exploded perspective view of the same rotary code diskmounting structure. Referring to FIGS. 4A, 4B and 4C, when mountingrotary code disk 3 made from 3 mm thick glass and having a central hole30 on a spindle 2, the rotary code disk 3 is placed on the lappedsupport surface 20 of the spindle 2, a ring 4 is put on the head 25 ofthe spindle 2 projecting through the central hole 30 of the code disk 3,the ring 4 is depressed with a jig so that the tongues 41 of the ring 4are bent to fasten the code disk 3 temporarily on the support surface20, the code disk 3 is centered with a microscope while the spindle 2 isrotated, and then the ring 4 is buried in an adhesive J to fasten thecode disk 3 to the spindle 2.

This conventional rotary code disk mounting structure fastens the codedisk 3 to the spindle 2 by bonding a portion of the upper surface of thecode disk 3 around the central hole 30 and the outer circumference ofthe projecting head 25 with the adhesive J. Therefore, the diameter D₀of the head 25 must be comparatively large to secure a desired fasteningstrength, and thus the diameter of the center hole 30 of the code disk 3must be comparatively large. The center hole 30 reduces the impactstrength of the glass code disk 3, and thus the code disk 3 providedwith the center hole 30 must be comparatively thick. Furthermore, thecode disk 3 provided with the center hole 30 requires an additionalprocess for forming the center hole 30.

The present invention is intended to eliminate the foregoingdisadvantages by employing a novel mounting structure.

SUMMARY OF THE INVENTION

As shown in FIGS. 1 and 2A, by way of example, a rotary code disk 3having no center hole is placed on the top surface 20 of a spindle 2provided with a central recess 21 and a plurality of peripheral cuts 22,and the central portion of the backside of the rotary code disk 3 isbonded to the top surface 20 by an adhesive J contained in the recess21.

Since the rotary code disk is not provided with a center hold such asthe center hole 30 of the conventional rotary disk (FIG. 4C), thestrength of the rotary disk of the present invention is higher than theconventional rotary code disk having a thickness the same as that of theformer.

Also the omission of a process of forming a central hole in the codedisk 3 and the ring 4 for temporarily fastening the code disk to thespindle rationalizes the, code disk fabricating and assemblingprocesses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation showing a rotary code disk mounting structureembodying the present invention;

FIG. 2A is an exploded perspective view of the rotary code disk mountingstructure of FIG. 1;

FIG. 2B is a sectional view of an essential portion of the rotary codedisk mounting structure of FIG. 1;

FIG. 3 is a view of assistance in explaining a manner of centering inaccordance with the present invention;

FIG. 4A is a side elevation of a conventional rotary code disk mountingstructure;

FIG. 4B is a sectional view of an essential portion of the rotary codedisk mounting structure of FIG. 4A; and

FIG. 4C is an exploded perspective view of the rotary code disk mountingstructure of FIG. 4A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Example 1

As shown in FIGS. 1 and 2A, rotary code disk 3 has the same size andshape as the conventional rotary code disk, except that the rotary codedisk 3 is not provided with a center hole.

A flange 1 is of a conventional type. A spindle 2 has a lapped mountingsurface 20 of 20 mm in diameter provided with a central circular recess21 of 14 mm in diameter and 0.3 mm in depth, and three cuts 22 formed ina mounting surface surrounding the circular recess 21 at equal angularintervals. The spindle 2 was put on a pulley 51 of a centering stand 5with a center recess 10 formed in the bottom surface thereof receiving acenter projection 50 formed on the pulley 51 as shown in FIG. 3. Anappropriate amount of an epoxy adhesive (Trade name: Araldyte AV 138)was put in the central portion of the recess 21 formed in the topsurface of the spindle 2 as shown in FIG. 2B. The code disk 3 was placedon the mounting surface 20 of the spindle 2, and then a rubber presserblock 62 was pressed through a spring 63 against the code disk 3 byturning the knob 61 of a pressing jig 6. When the backside of the codedisk 3 was pressed firmly against the lapped mounting surface 20 of thespindle 2, a portion of the adhesive J was forced outside the recess 21through the cuts 22. Then the code disk 3 was centered by observing thecode disk 3 with a microscope along a direction indicated by the arrowV, while the pulley 51 was rotated through a belt b. After centering thecode disk 3, the pressing jig 6 was set to keep the rubber presser block62 pressed through the spring 63 against the code disk until theadhesive J solidified.

Although the amount of the adhesive J used was somewhat greater than thevolume of the recess 21, the surplus portion of the adhesive J waspressed outside the recess 21 through the cuts 22, which also serve asair escapes. Therefore, the adhesive J did not penetrate between thecode disk 3 and the mounting surface 20 of the spindle 2, and the codedisk 3 was fastened adhesively to the mounting surface 20 of the spindle2 with the backside thereof in precise contact with the mounting surface20.

Example 2

The process of putting the adhesive J in the recess 21 of the spindle 2as in Example 1 was omitted. That is, the spindle 2 and the rotary codedisk 3 were set on the centering stand 5 as shown in FIG. 3 withoutputting the adhesive J in the recess 21 of the spindle 2, the rotarycode disk 3 was centered with the rubber presser block 62 of thepressing jig 6 pressed through the spring 63 against the rotary codedisk 3, an epoxy adhesive was injected through the cuts 22 into therecess 21 with a syringe, not shown, to fill up the recess 21 and thecuts 22 with the epoxy adhesive, and then the adhesive was solidified.

The code disk 3 is centered by tapping the rim of the code disk 3 with ahammer observing the runout of the code disk 3 while the spindle isturned slowly. Since the code disk 3 is centered before the adhesive isput in the recess 21 in Example 2, the adhesive J does not wet thelapped mounting surface and the backside of the code disk even if thecode disk is shifted in the centering process by a considerably largedistance in a plane relative to the spindle. Accordingly, the centeringwork is simplified and the code disk 3 can be precisely mounted on themounting surface and is fastened adhesively to the mounting surfacewithout allowing the adhesive J to enter between the backside of thecode disk 3 and the lapped mounting surface 20 of the spindle 2.

Modification

When the adhesive injecting means employed in Example 2 is used, radialgrooves 22 formed in the lapped mounting surface of the spindle 2 as onetype of the recess 21 facilitate the injection of the adhesive.

What is claimed is:
 1. A rotary code disk mounting structure for anoptical encoder, comprising:a flange; a spindle mounted on a top surfaceof said flange, said spindle having defined on a top end thereof acentral circular recess; and a rotary code disk adhesively mounted onsaid spindle, said rotary code disk having an adhesive substance fillingthe circular recess for adhering said rotary code disk to said spindle.2. A rotary code disk mounting structure for an optical encoder as setforth in claim 1, wherein said spindle has further defined on the topend at least one radially extending cut forming an opening between thecircular recess and an outside surface of said spindle.
 3. A rotary codedisk mounting structure for an optical encoder made from the processwhich includes the steps of:forming a spindle on a top surface of aflange; forming on a top end of said spindle of a central circularrecess; filling the central circular recess with an adhesive substance;mounting a rotary code disk on the top end of said spindle to cover thecircular recess; and applying pressure to said rotary code disk for atime period so as to allow the adhesive substance to solidify.
 4. Arotary code disk mounting structure for an optical encoder as set forthin claim 3, said mounting structure being made from the further stepof:forming on the top end of said spindle at least one radiallyextending cut forming an opening between the circular recess and anoutside surface of said spindle.
 5. A rotary code disk mountingstructure for an optical encoder as set forth in claim 4, said mountingstructure being made from the further step of:filling the circularrecess with the adhesive substance through the radially extending cutafter mounting said rotary code disk on said spindle.